Hacettepe Üniversitesi Eğitim Fakültesi Dergisi 18 : 79 - 84 [2000]
FRESHMAN
STUDENTS'
MISCONCEPTIONS
EQUIlIBRIUM
IN CHEMICAl
Arzu (Özdemir) ERDEMİR*. Ömer GEBAN** and Esen UZUNTİRYAKİ***
ÖZET:
Bu çalışmanın amacı üniversite birinci sınıf öğrencilerının kimyasal denge kenusundaki kavram yanılgılarını belirlemektir. Bu çalışma. i 43 Biyoloji. Biyoloji
Öğretmenliği. Fizik ve Fizik Öğretmenliği Bölümü öğrencilerinin katılımıyla i 998- i 999 bahar döneminde ODTÜ'
de gerçekleştirilmıştIr. Kimyasal Denge Kavramları Başarı
Tesıi tüm öğrencilere uygulanmıştır. Sonuçlar. bir çok öğreneınin denge şartlarının değişınesi. tepkime hızı ile denge arasındaki ilişki ve tepkime hızı ve tepkime kavramı
hakkında kavram yanılgısı oldut,unu göstermıştır.
ANAHTAR
SÖZCÜKLER:
Kavram
Yanılgısı,
Kimyasal
Denge, Kimya Eğiıimi.
ABSTRACT:
The purpose of this study was to investigate the misconceptions of freshman students in chemical
equilibrium, In this study, 143 freshman students from
Biology,
Biology
Education,
Physics
and Physics
Education Departments in MEl'U took part during 19981999 spring semester. Chemical Equilibrium Concepts Achievement Test was administered to all subjects, The
results showed that many students had misconceptions
about changing equilibrium conditions. relating rate and
equilibrium and rate vs, extent.
KEY
Chemisıry
WORDS:
Misconcq tion, Chemical Equilibrium,
Educarion
1. INTRODUCTION
The purpose of this study was
the misconceptions of Freshman
Biology,
Biology
Education,
Physics Education Depac1:ments
chemical equilibrium.
to investigate
students from
Physics and
in METU in
Many students at alllevels struggle to learn
chemistry, but are often unsuccessful. One possible answer is that many students do not construct appropriate unders! andings fundamental
chemical concepts from the very beginning of
their studies (1), Therefore, they cannot fully understand the more advanced concepts that build
upon the fundamentals.
Researchers have documented the fact that
students often have naive ideas about how the
world works, which hinder the learning of scientific ex planations (2,3), It is clear that students
use preexisting conceptions constructed from
reflection on previous experiences to reason
about newly presented science concepts, and to
make sense of their instructional science experiences (4,5) Such preconceptions are often
incorrect from a scientific viewpoint and can interfere with students' learning of science (4,6,7).
Some student misconceptions are very resistant
to instructional change and some students persist
in giying answers consistent with their misconceptions even after large amounts of instruction
(4,8,9,10,11,12),
What a student leams, therefore, results from the interaction between what
is brought to the leaming situation and what is
experienced while in it (13).
A review of literature reveals that there are
four topic s within the domain of chemistry that
give leamers most difficulty: chemical equilibrium, the mole, reaction stoichiometry and oxidation-reduction
(14), Of these, chemical
equilibrium concept is regarded as the most difficult concept for students to comprehend (15),
Because the topic s are very abstract and some
words from everyday language are used with
different meanings.
Children go through four stages of intellec-
Res. Ass., METU Faculty of Education, Secondary Science and Mathematics Education Department., ANKARA
erdemir@tutor,fedu,metu.edu.tr
Assoc. Prof. Dr., METU Facult y of Education, Secondary Science and Mathematics Education Department., ANKARA
**
[email protected]
*
*** Res. Ass., METU Faculty of Education, Secondary Science and Mathematics Education Department.,
[email protected]
ANKARA
80
tual development starting at the sensory-motor
phase, through the preoperational and concrete
operational stages, to the form al operational
phase when abstract thinking becomes possible
(16). Although Piaget claimed that the formal
operational phase would be .ıttained at the age of
13 to 17 years, the rate at which children pass
through the four phases vanes. Thus, many students may not be able to deal with the cognitive
transformations associated with abstract reasoning and may still require concrete example
before concepts can be grasped (17).
The concept of "chemical equilibrium" includes alabel that is known lo students attending
chemistry classes and for which they have a
preconception. This preconception stems from
the label "equilibrium" being used in physics as
well as in some everyday life balancing situations such as circus acrobatics, bicycle riding, or
weighing balance. The labd "equilibrium" acquires attributes that are ch aracteristic of these
situations. Attributes of equality in general,
equality of two sides, stability, and a static
nature become associated with the concept of
equilibrium (18). However, these attributes of
equilibrium are the very ones that actually differentiate between physical and chemical
equilibrium. Phenomena that reach chemical
equilibrium appear naturall) macroscopically as
stable and static systems. On the other hand, on
the microscopic level the system is dynamic not
only because of molecular movement but als o
because the process of breaking and creating
bonds go on with the net result of zero. Attributing macroscopic qualities to the microscopic level leads to miscorıceptions in the understanding of the concepl 'chemical equilibrium". (19)
Bergquist and Heikkinen (1990) have pointed out that equilibrium is fundamental to the
understanding of acid- base behavior, oxidationreduction reactions and solubility. (20) Mastery
of the concepts associated with equilibrium
facilita<es mastery of the other chemical concepts.
[EdJ. 18of
Arzu (Özdemir) Erdemir. Ömer Geban. Esen Uzuntiryaki
The following is the table of misconceptions
of students in chemical equilibrium which ıs
derived from review of related literature:
i. Approach To Equilibriurn
a) The rate of forward reaction ıncreases
with time from mixing reactants until equilibrium is established
b) Reverse reaction rate is the same as the
forward rate
II. Characteristics of Chernical Equilibrium
a) There is a simple arithmetic relationship
between the concentrations of reactants and
products such as [reactants]=[products]
at
equilibrium
b) Forward
reaction must be completed
before reverse reaction starts
c) Lack of awareness to the dynamic nature
of the chemically equilibrated state, equilibrium
is seen as the firmly hel d concept of a static twosided picture
d) Concentrations fluctuate as equilibrium is
established
IV. Changing
Equilibriurn
Conditions
i. Effect on concentrations
a) Addition of more reactant changes only
the product concentrations
b) Uncertainty how a temperature, volum e
or pressure change will alter the equilibrium
concentrations
ii. Relating Rate and Equilibrium
If a system at equilibrium is disturbed by
some change, the system will shift so as to partially counteract the effect of change. The rate of
the reaction to which the equilibrium shifts will
be greater when a new equilibrium is established.
iii. Effeet on equilibrium constant
a) Equilibrium
constant
while at constant temperature
varıes LO value
8]
Freshman Students' Misconceptions in Chemical Equilibrium
b) When the temperature is increased and
equilibrium is re-established the equilibrium
constant is the same as nnder the initial conditions
c) Value of equilibrium constant changes
with amounts of products or reactants
d) Value of equilibrium constant changes
with volume
e) Value of equilibrium constant changes
with pressure
o Value
of equilibrium constant increases if
a catalyst is used
iv. Effect of a catalyst
a) A catalyst can affect the rates of forward
and reverse reactions differently
b) A catalyst leads to a higher yield of product
V. Reversibility vs. Completion
A reaction is reversible yet goes to completion that is no discrimmation between reactions that goes to completion and reversible
reactions
VI. Rate vs. Extent
Failure to distinguish between rate (how
fast) and extent (how far) of reaction
VII. Mass vs. Concentration
a) Uncertainty when to use volume
b) Confusion regarding amount (moles) and
concentration (molarity)
4. METHOD
2.1 Subjects
In this study, 143 fre~hman students taking
General Chemistry course (Chem 102) in 19981999 spring semester took part. Chem- 102 course includes ehemica! equi librium ehapter. Af ter
students covered this chapter, Chemical Equilibrium Concepts Achievement Test was administered. The distribution of students according to
departments is as follows:
Table ı. Distribution of subjects with respect to
departments
Department
Count
Biology
30
Biology Education
30
Physics
38
Physics Education
45
2.2 Instruments
In this study, Chemical Equilibrium Concepts Achievement Test was administered to all
subjects. This test was developed by Geban and
Özdemir. It consisted of 25 multiple choice
questions. Both English and Turkish versions of
the test were given to students at the same page
because some students have taken chemistry
course in Turkish in high school. During the
development stage of the test, firstly, the instructional objectives were determined. Secondly, the
literature related to students' misconceptions
with respect to chemical equilibrium was carefully examined. Each distracter of an item was
prepared in such a way that it was confronted
with students' misconceptions. The items were
evaluated by a group of classroom teachers and
experts in science education and chemistry for
the appropriateness of the items and the content
validation. The reliability of the test was found
to be 0.80.
Some items from the Chemical Equilibrium
Concepts Achievement Test:
Consider an equilibrium mixture:
2NO(g) + CI2(g)
-
2NOCl(g)
+ heat
at
200°C and 1 atm pressure.
Indicate the new situation ın each of the
items by marking the appropriate letter on the
, J.of
A,ZU (Özdemir) Erdemir' Ömer Geban . Esen Uzuntiryaki
82
LFO:d 18
right side of the sentences by usıng the following key:
A: greater than that in the initial equilibrium;
B: less than that in the irıitial equilibrium;
A) 0.5+0.25x
D: data insufficient for conclusion
1. Some C12 is removed from the system, the
volume and the temperature being kept
constant, When the system returus to another equilibrium,
(a) The rate at which NO is being formed
will be .....
(b) The concentration of NOCl present will
be .....
(c) The equilibrium constant will be .....
-.
2. 2CO(g) + 02(g)
2C02(g) + heat
reaction is at equilibrium. Which one of the following increases the concentration of CO2 gas?
A) Decreasing the conce'ntration of CO gas
B) Decreasing the concentration of O2 gas
C) U sing a catalyst
D) Increasing the temperature
E) Increasing the pressure
For the reaction
A2(g) + 2B2(g)
which one of the following is true?
i. At equilibrium, [A2] =
=
II. At equilibrium the rate of forward and
reverse reactions are equal to zero
III. At equilibrium
gases are constant
A) Only i
the concentrations
B) Only II
D) i and II
Suppose 1 mo le of each of three gases are
mixed and allowed to reach equilibrium by the
conversion of "x" moles of NH) gas into Hz and
N2 gases in a 2 liters container. What is the
molar concentration of Nz at equilibrium?
c: same as that in the initial equilibrium;
3.
2C(g)
2NHlg)
of
c) Only III
E) I, II and III
4. Considerthe following equilibriumsystem:
B) l+O.5x
D) 1+0.25x
C) 0.5+0.5x
E) 1+x
3. RESULTS
Statistical analyses were carried out by
SPSS, Statistical Package for Social Sciences
for Personal Computers. Students' correct
proportions to questions were caleulated.
By giving 1 point for each question and subquestion, students' total scores were found. The
scores varied from 7 to 31 out of 35. The mean
of total scores was found to be 22,41 .
For the question related to changing equilibrium conditions the correct proportion was
found to be 0,19. Students think that a catalyst
leads to higher yield of product. Students have
uncertainty how a temperature, volume or pressure change will alter the equilibrium concentrations.
Only 40% of the students answered correctly
to the questions in which they were asked to find
the equilibrium concentration of species. In order to solve these questions, they had to convert
given moles to molarities. But many of the students confused the amount (moles) and concentration (molarity).
Moreover, students had difficulty in relating
rate and equilibrium. They think that if a system
at equilibrium is disturbed by some change, the
system will shift so as to partially counter act the
effect of change and the rate of the reaction to
which the equilibrium shifts will be greater
when a new equilibrium is established. The correet proportions for these questions were found
to be 0,60, 0,45 and 0,50 respectively.
Freshman Students' Misconceptions
In addition, 80% of the students failed to distinguish between rate (how fast) and extent (how
far) of reaction.
4. DISCUSSION
The purpose of this study was to investigate
the misconceptions of Freshman students from
Biology,
Biology
Education,
Physics and
Physics Education Departments in METU in
chemical equilibrium.
Generally, students so]ve problems successfully using memorized algorithms. Many students who may be succe~sful at solving mathematical problems do not understand the chemical concepts behind their memorized algorithmic solutions.
Many students exhibit misconceptions in
several content areas in chemistry. One of these
areas is the chemical equilibrium since firstly,
the concepts are seen abstract and secondly, the
words from everyday
language are used but
with different meanings. Statements of equilibrium concepts contain ev~ryday terms such as
shift, equal, stress and balanced. Such vocabulary can lead to very different visual images. For
this reason, the different attributes of equilibrium and chemical equilibrium must be analyzed
and presented to overcome the confusion of
these concepts.
Some misconceptions regarding chemical
equilibrium might be the result of instruction
that emphasis correct concepts without highlighting common conceptual errors. Chemistry teachers should be aware of students' the prior
know ledge and misconceptions. They should
examine why misconceptions occur and use
leaming activities to eliminate misconceptions.
Because, it is very difficlılt to remove misconceptions from the minds of the leamers.
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